Distribution of ULF energy (ƒ < 80 mHz) in the inner magnetosphere: A statistical analysis of AMPTE CCE magnetic field data

1992 ◽  
Vol 97 (A7) ◽  
pp. 10751 ◽  
Author(s):  
Kazue Takahashi ◽  
Brian J. Anderson
Keyword(s):  
Magnetic Field ◽  
Statistical Analysis ◽  
Field Data ◽  
Magnetic Field Data ◽  
Inner Magnetosphere

scholarly journals Comprehensive survey of Pc4 and Pc5 band spectral content in Cluster magnetic field data

2009 ◽  
Vol 27 (8) ◽  
pp. 3237-3248 ◽  
Author(s):  
L. B. N. Clausen ◽  
T. K. Yeoman
Keyword(s):  
Magnetic Field ◽  
Field Data ◽  
Spectral Content ◽  
Magnetic Field Data ◽  
Inner Magnetosphere ◽  
Field Line Resonances ◽  
Spectral Peaks ◽  
Comprehensive Survey ◽  
Compressional Mode ◽  
Field Lines

Abstract. In the first part of this study we present two case studies of pulsations that, with the help of ground-based data, are identified as field line resonances (FLRs). These pulsations occurred at frequencies which belong to a set of frequencies that has been suggested to be preferred in the terrestrial magnetosphere (CMS frequencies). We go on to show that for both events there is a significant signature at the same frequency in the time series of the compressional magnetic field observed by the conjugate Cluster satellites. We interpret these as signatures of the compressional mode driving the FLRs. In the second part we present a statistical study including one year's worth of Cluster magnetic field data. For each orbit between May 2004 and June 2005 we identified a three hour interval during which the satellites were located on closed magnetic field lines. We identified peaks in the spectrum between 1.0 and 15.0 mHz of the compressional, poloidal and toroidal components of the magnetic field. We use this database of spectral peaks observed on closed magnetic field lines to investigate whether peaks occur at a preferred set of frequencies which would be indicative for the Earth's magnetosphere behaving like a cavity/waveguide. We find no consistent preference for all CMS frequencies in our dataset, however we do find a preference for certain higher frequencies suggesting that higher harmonics of the cavity/waveguide are a persistent feature of the inner magnetosphere, and are detected by the Cluster spacecraft. This result could be explained by the polar orbit of the Cluster satellites.

scholarly journals Comparison of eight years magnetic field data from Cluster with Tsyganenko models in the inner magnetosphere

2010 ◽  
Vol 28 (1) ◽  
pp. 309-326 ◽  
Author(s):  
Q.-H. Zhang ◽  
M. W. Dunlop ◽  
R. Holme ◽  
E. E. Woodfield
Keyword(s):  
Magnetic Field ◽  
Field Data ◽  
Ring Current ◽  
Early Years ◽  
Magnetic Field Data ◽  
Inner Magnetosphere ◽  
External Conditions ◽  
Pass Through ◽  
Best Fit ◽  
Current Systems

Abstract. Eight years of magnetic field data, taken while the four Cluster spacecraft pass through, or adjacent to, the equatorial ring current, have been surveyed to investigate the effects on the Earth's magnetic field of the externally driven current systems connecting the ionosphere, cusp and ring current regions. This study extends previous work to cover a greater range of orbit location and external conditions. We compare the modeled magnetic field from different global field models (Tsyganenko, 1989, 1996, and 2001, hereafter T89, T96 and T01) with data from the four Cluster spacecraft. Comparing with the different models allow us not only to characterize each model's performance, but also provides insight into the physical sources of observed signals. The data generally deviate much less from the expected model field during the years close to the solar minimum, implying that the models perform better during weaker geomagnetic activity. There are particular deviations from the models associated with the ring current (well-defined smooth trends) and region 2 field aligned currents (FACs) or low-altitude cusp FACs (sharp bipolar signatures). During the ring current crossings (through perigee, at 4–5 RE), the T96 model always overestimates the ring current, while the T01 and T89 models sometimes underestimate it. The sharp bipolar signatures are not always sampled, implying a localized extent, but only the T96 and T01 models include forms for the region 2 FACs and T01 appears to model these better. Overall, all deviations from T01 are much smaller than for the other models, indicating that this model achieves the best fit to the data. The 4 Cluster spacecraft observe nearly the same signatures at small separations (during the early years of the mission) but do sample different signatures at the large separations (during the later years). Using the four-spacecraft technique, we infer that the region 2 FACs, with a transverse thickness of ~0.17–0.54 RE, and cusp FACs, with a thickness of ~0.06–0.12 RE, are very stable in size and location.

An Augmented Iteratively Re-weighted and Refined Least Squares Method for lp Minimization Problem in Inverse Modeling of Potential Field Magnetic Data

2020 ◽  
Vol 1 (3) ◽  
Author(s):  
Maysam Abedi
Keyword(s):  
Magnetic Field ◽  
Magnetic Susceptibility ◽  
Least Squares ◽  
Minimization Problem ◽  
Potential Field ◽  
Field Data ◽  
Least Squares Method ◽  
Porphyry Copper ◽  
Magnetic Data ◽  
Magnetic Field Data

The presented work examines application of an Augmented Iteratively Re-weighted and Refined Least Squares method (AIRRLS) to construct a 3D magnetic susceptibility property from potential field magnetic anomalies. This algorithm replaces an lp minimization problem by a sequence of weighted linear systems in which the retrieved magnetic susceptibility model is successively converged to an optimum solution, while the regularization parameter is the stopping iteration numbers. To avoid the natural tendency of causative magnetic sources to concentrate at shallow depth, a prior depth weighting function is incorporated in the original formulation of the objective function. The speed of lp minimization problem is increased by inserting a pre-conditioner conjugate gradient method (PCCG) to solve the central system of equation in cases of large scale magnetic field data. It is assumed that there is no remanent magnetization since this study focuses on inversion of a geological structure with low magnetic susceptibility property. The method is applied on a multi-source noise-corrupted synthetic magnetic field data to demonstrate its suitability for 3D inversion, and then is applied to a real data pertaining to a geologically plausible porphyry copper unit.  The real case study located in  Semnan province of  Iran  consists  of  an arc-shaped  porphyry  andesite  covered  by  sedimentary  units  which  may  have  potential  of  mineral  occurrences, especially  porphyry copper. It is demonstrated that such structure extends down at depth, and consequently exploratory drilling is highly recommended for acquiring more pieces of information about its potential for ore-bearing mineralization.

scholarly journals A reexamination of “interstellar ion waves” previously identified in Pioneer 10 magnetic field data

1998 ◽  
Vol 25 (19) ◽  
pp. 3721-3724 ◽  
Author(s):  
Neil Murphy ◽  
Edward J. Smith ◽  
Joyce Wolf ◽  
Devrie S. Intriligator
Keyword(s):  
Magnetic Field ◽  
Field Data ◽  
Magnetic Field Data ◽  
Ion Waves ◽  
Pioneer 10

Using an induction coil sensor to indirectly measure the B-field response in the bandwidth of the transient electromagnetic method

Geophysics ◽  
2000 ◽  
Vol 65 (5) ◽  
pp. 1489-1494 ◽  
Author(s):  
Richard S. Smith ◽  
A. Peter Annan
Keyword(s):  
Magnetic Field ◽  
Field Data ◽  
Indirect Measurement ◽  
Rate Of Change ◽  
Induction Coil ◽  
Voltage Response ◽  
Magnetic Field Data ◽  
Transient Electromagnetic ◽  
Different Characteristics ◽  
The Magnetic Field

The traditional sensor used in transient electromagnetic (EM) systems is an induction coil. This sensor measures a voltage response proportional to the time rate of change of the magnetic field in the EM bandwidth. By simply integrating the digitized output voltage from the induction coil, it is possible to obtain an indirect measurement of the magnetic field in the same bandwidth. The simple integration methodology is validated by showing that there is good agreement between synthetic voltage data integrated to a magnetic field and synthetic magnetic‐field data calculated directly. Further experimental work compares induction‐coil magnetic‐field data collected along a profile with data measured using a SQUID magnetometer. These two electromagnetic profiles look similar, and a comparison of the decay curves at a critical point on the profile shows that the two types of measurements agree within the bounds of experimental error. Comparison of measured voltage and magnetic‐field data show that the two sets of profiles have quite different characteristics. The magnetic‐field data is better for identifying, discriminating, and interpreting good conductors, while suppressing the less conductive targets. An induction coil is therefore a suitable sensor for the indirect collection of EM magnetic‐field data.

scholarly journals The geomagnetic field at 1982 from DE-2 and other magnetic field data.

1988 ◽  
Vol 40 (9) ◽  
pp. 1103-1127 ◽  
Author(s):  
R. A. LANGEL ◽  
J. R. RIDGWAY ◽  
M. SUGIURA ◽  
K. MAEZAWA
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Field ◽  
Field Data ◽  
Magnetic Field Data
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